This disclosure related to active power filters. According to one exemplary embodiment, this disclosure provides active power filter methods and apparatus for power factor (PF) and harmonic control of a power supply associated with a printing device.
The primary purpose of a power filter is to control the PF associated with the powered device. The PF is the ratio of real power to apparent power, where the ideal PF is equal to 1. As a practical matter, the PF associated with a load (i.e. the power supply and the device powered by the power supply) is a metric which indicates the percentage of supplied power actually being used to operate the device.
Another purpose of a power filter is to reduce the harmonic components associated with the input current and voltage. Typically, loads are not completely resistive because of the capacitive and inductive nature of the powered devices. Consequently, harmonics are generated which shift the input voltage and current out of phase. These harmonics can also contribute to reducing the efficiency of the powered device.
To improve the PF and harmonic control of powered devices, it is common to use passive filters and active filters operatively connected to the power supply associated with the device. Commonly, passive filters are used because of their simplicity. Passive filters are primarily composed of passive elements, such as capacitors and inductors, which offset the advance or lag of the current phase to reduce the harmonics associated with the device.
One disadvantage associated with passive filters is the need for relatively large components for dealing with large currents and voltages.
There is a need for active power filters to accommodate large currents and voltages to reduce the component sizes necessary to control the PF and harmonics associated with a powered device, such as a printing device.